1. Field of the Invention
This invention relates to a method of producing low-cholesterol butter fat by vapor sparging, and to the low-cholesterol butter fat product produced by the method.
2. Description of Related Art
Milk fat-containing foods are popular with consumers. Consumers prize the distinctive organoleptic properties of milk fat. For example, butter, which contains 80 percent milk fat, is highly prized for its properties as a condiment. However, milk fat and all other animal fats contain the sterol cholesterol. Recently, excessive dietary fat and cholesterol consumption have been strongly linked to human health issues, particularly coronary heart disease. Some consumers have therefore become hesitant about utilizing cholesterol-containing products.
Others have recognized the desirability of reducing the cholesterol content of animal fats, including milk fat. However, most processes for cholesterol reduction produce products having organoleptic properties which typically differ significantly from the properties of the natural product. For example, mouth feel, melting point, or color may be significantly altered by the cholesterol removal technique. A satisfactory cholesterol removal process must maximize the removal of cholesterol and minimize alterations to the properties of the cholesterol-containing product to yield a low-cholesterol product indistinguishable from fresh, natural product.
Methods for deodorizing and stabilizing oils are also known. Some of these methods remove sterols from oil, as noted in U.S. Pat. No. 2,613,215. This patent discloses a method which removes "unsaponifiable materials," together with free fatty acids, from oil. After partial hydrogenation, the unsaponifiable materials are removed by high temperature fractionation with a liquified, normally-gaseous hydrocarbon solvent. This patent also discloses that polar solvents can be utilized to separate unsaponifiable materials, which are soluble in the solvent, from the major portion of the oil, which is substantially immiscible in polar solvent. The thus-treated oil is further "deodorized," essentially as taught in U.S. Pat. No. 2,351,832, i.e., by injecting steam at a temperature above 250.degree. C. through the oil at a pressure of less than about 20 millimeters of mercury. Deodorization, as taught in this patent, is unsatisfactory for removing cholesterol from animal fat not only because cholesterol removal is low but also because losses of lower molecular weight glycerides (mono-, di-, and tri-glycerides) are significant. Loss of these lighter glycerides adversely affects the organoleptic characteristics of butterfat, giving the product a waxy mouth feel.
Fractionation of fats has been used to obtain separate component portions, typically so that the portions can be selectively recombined to yield a product having pre-selected characteristics. For example, the solvent-assisted fractionation disclosed in U.S. Pat. No. 4,005,228 is utilized to separate butter fat into fractions by melting point, i.e., melting point less than 0.degree. C., between 0.degree. and 20.degree. C., and above 20.degree. C. The high- and low-melting fractions are combined to yield a dairy spread.
Supercritical extraction has also been utilized to modify various foodstuffs, including butter, as described in U.S. Pat. No. 4,504,503. However, one of the drawbacks to this technique is that conditions which maintain the solvent in the supercritical region typically involve extremes of temperature and pressure. Therefore, the equipment required is expensive. For example, in this patent, the preferred temperature range is from 40.degree. to 250.degree. C., while the preferred pressure range is from 100 to 400 bar.
British patent specification 1,559,064, an improvement of GB 1,525,315, discloses the use of molecular distillation to reduce the cholesterol content of a medium containing fats. After degassing, anhydrous fat is subjected to molecular distillation at a pressure less than 0.005 Torr to remove the unsaponifiable fraction, which contains the sterols. Then, in accordance with the method of GB 1,525,315, an aqueous medium having a viscosity of from 2000 to 20,000 cp measured at a temperature between 20.degree. and 30.degree. C. is mixed into the treated fat at a temperature between 15.degree. and 45.degree. C. to produce a butter-like product.
Both U.S. Pat. No. 2,613,215 and EP 0 174 848 A2 teach that cholesterol can be removed from fats by contacting the fat with a solid absorbent or adsorbent material. Silica gel and activated carbon are utilized as examples of appropriate material.
Shishikura, "Modifications of Butter Oil by Extraction with Supercritical Carbon Dioxide", 50 Agric. Biol. Chem. 1209 (1986), notes that supercritical fluid extraction using carbon dioxide is useful for fractionation of triglycerides in butter oil according to carbon number, but that this technique does not separate cholesterol from the triglycerides. Instead, butter oil was contacted with supercritical carbon dioxide and silica gel. However, this technique not only lowered the cholesterol level, but also affected the triglyceride distribution. Thus, the technique is unsatisfactory, because the composition and spreadability are affected.
The above-described methods for cholesterol removal are unsatisfactory. Known steam deodorization techniques are feasible for deodorization because of the great differences between the volatility of triglycerides and the volatility of substances which give oils their distinctive flavors and odors. However, for removal of cholesterol from butter fat, one must look at the volatility difference between cholesterol and the substances which give butter its distinctive organoleptic characteristics. The volatility difference between the mono- and di-glycerides and lower molecular-weight triglycerides and cholesterol is relatively small. Both the presence of some mono-and di-glycerides in butter fat and the unique triglyceride composition make important contributions to the mouth feel of butter. Alteration of the concentration of these components in butter fat and the relative proportions thereof yields unacceptable mouth feel.
Modifications to the steam-sparging processes also fail as cholesterol removal techniques. For example, U.S. Pat. No. 2,407,616 teaches that heating the vapor from a steam sparging deodorization process prevents condensation and reflux of vaporized impurities. With respect to mono- and di-glycerides from butter fat, this would merely ensure that these components are removed from the treated butter fat. Another method which virtually assures that all the volatiles are removed is taught in U.S. Pat. No. 2,759,883. This patent discloses that creation of a thin film of oil both when the oil is first exposed to vacuum and after heating enhances the removal of volatile components.
It is an object of this invention to provide a method for producing a low-cholesterol butter fat product by sparging.
It is another object of this invention to provide a method for producing a low-cholesterol butter fat product by multi-stage sparging wherein at least the last stage utilizes steam as the sparge medium at process conditions which promote partial hydrolysis of triglycerides to free fatty acids and mono- and di-glycerides to substantially restore the composition of the low-cholesterol product to that of natural butter fat.
It is a further object to this invention to provide a method for producing a low-cholesterol butter fat product by sparging, under vacuum, while applying heat to the walls of a vapor space above the mass during sparging.
It is another object of this invention to provide products produced by these methods.